Here are some basic wheel tyre combinations that can fit, if you have any more post them below.

PCD = 114.3mm Offset = 45mm

Standard Rim f/r = 17"x7"
Standard Tyre f/r = 215/45-17
(A -40mm drop is possible with this combination)

18" upgrade f/r =18"x7 1/2"
18" upgrade f/r =225/40/18
18" upgrade f/r =18"x8"
18" upgrade f/r =225/40/18
18" upgrade r =18"x8.5"
18" upgrade r =255/35-18
(A -30mm drop is possible with these combinations, however minor arch rolling is needed with the 255/35 combination)

19" upgrade f/r =19"x8"
19" upgrade f/r = 235/35-19
(A -25mm drop is possible with these combinations)
With 19's don't run any rim bigger than 8" on the front as it will hit the strut.19's will rub on the front inner arch at full lock, but this can be solved by cutting or bending away some of the plastic trim.

Of course for the nutter out there even a -60mm drop is possible with 19's.....................you know who you are!!!!:P

Rolling radius is something you have to always remember, but due to the fact that it is not possible to buy every size of tyre, (without shares in Microsoft!) remember you must try and keep the rolling radius within +/- 4% of the original.
This link will help. http://www.dakota-truck.net/TIRECALC/tirecalc.html

Always remember anyone can fit big wheels and park up at a show, just remember living with them every day is a whole lot more work!

With anything bigger than 19's I would sugest an arch extension kit. This would bring them away from the inner arch to provide clearence.

OFFSETS

FRONT


width | offset | tires range (width)
7 = 40 and up 215-225
7.5 = 42 and up 215-235
8 = 43 and up 215-235
8.5 = 45 and up 215-225

REAR


7 = 40 and up 215-225
7.5 = 40 and up 215-235
8 = 42 and up 215-245
8.5 = 45 and up 225-265 (255-265 requires rolling or having lip)
9 = 49 and up 235-275 (MAY require rolling or shaving lip)
9.5 = 52 and up 245-285 (MAY require rolling or shaving lip, 285 may require more modification)
10 = 45 and up 255-315(requires pulling fender)

Four or five stud? Please say five!

5

Excellent. Means I can keep my Pro Race 1.2s if I get a IS200!

i'm guessing these et's are based on a minimum so they dont foul the struts, anyone have any idea what the maximum et you can so they dont stick out past the wheel arches?

As you can see from above, it depends on what wheel size your after

Wow, this is all greek to me.

I'm looking at getting a set of 17" or 18" alloy wheels for an IS250 and by the looks of this I will have to get them professionally fitted as I have no bloomin' idea what the above posts mean!

Interestingly, not many websites offer wheels for the IS250. Plenty offer them for the IS200 but I am unsure if the dimensions of the wheels, arches and so on will be the same, so I am reluctant to buy any.

I've trawled this forum looking for any posts that might help me but I either draw a blank or I find posts with information that makes no sense to me, a complete idiot when it comes to wheels.

I would be ever so grateful if someone could let me know if these wheels will fit and what size tyres I should be getting please?

Many thanks

HRD

Info about them here